33892 datasheet(24/28 Pages) FREESCALE

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33892

MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA

Loss of VDD

If the external 5.0 V supply is not within specification, or even

disconnected, all register content is reset. The outputs can still

be driven by the direct inputs IN[0:3]. The 33892 uses the

battery input to power the output MOSFET-related current

sense circuitry and any other internal logic providing fail-safe

device operation with no VDD supplied. In this state, the

watchdog, overvoltage, overtemperature, and overcurrent

circuitry are fully operational with default values.

Fault Mode

The 33892 indicates the faults below as they occur by driving

the FS terminal to [0]:

• Overtemperature fault

• Overvoltage and Undervoltage fault

• Open load fault

• Overcurrent fault (high and low)

The FS terminal will automatically return to [1] when the fault

condition is removed, except for overcurrent and in some cases

undervoltage.

Fault information is retained in the fault register and is

available (and reset) via the SO terminal during the first valid

SPI communication (refer to Table 10, page 22).

Overtemperature Fault (Non-Latching)

The 33892 incorporates overtemperature detection and

shutdown circuitry in the output structure. Overtemperature

detection is enabled when the output is in the ON state.

For the output, an overtemperature fault (OTF) condition

results in the faulted output turning OFF until the temperature

falls below the TSD(HYS). This cycle will continue indefinitely until

action is taken by the MCU to shut OFF the output, or until the

offending load is removed.

When experiencing this fault, the OTF fault bit will be set in

the status register and cleared after either a valid SPI read or a

power reset of the device.

Overvoltage Fault (Non-Latching)

The 33892 shuts down the output during an overvoltage fault

(OVF) condition on the VPWR terminal. The output remains in

the OFF state until the overvoltage condition is removed. When

experiencing this fault, the OVF fault bit is set in the bit D1 and

cleared after either a valid SPI read or a power reset of the

device.

The overvoltage protection can be disabled through SPI (bit

OV_DIS). When disabled, the returned SO bit OD13 still reflects

any overvoltage condition (overvoltage warning).

Undervoltage Shutdown (Latching or Non-Latching)

The output latches OFF at some battery voltage between

4.75 V and 5.75 V. As long as the VDD level stays within the

normal specified range, the internal logic states within the

device will be sustained. This ensures that when the battery

level then returns above 5.75 V, the 33892 can be returned to

the state that it was in prior to the low VPWR excursion. Once the

output latches OFF, the outputs must be turned OFF and ON

again to re-enable them. In the case IN[1:0]=0, this fault is non-

latched.

The undervoltage protection can be disabled through SPI (bit

UV_DIS). When disabled, the returned SO bit OD14 still reflects

any undervoltage condition (undervoltage warning).

Open Load Fault (Non-Latching)

The 33892 incorporates open load detection circuitry on the

output. Output open load fault (OLF) is detected and reported

as a fault condition when the output is disabled (OFF). The

open load fault is detected and latched into the status register

after the internal gate voltage is pulled low enough to turn OFF

the output. The OLF fault bit is set in the status register. If the

open load fault is removed, the status register will be cleared

after reading the register.

The open load protection can be disabled trough SPI (bit

OL_DIS).

Overcurrent Fault (Latching)

The 33892 has eight programmable overcurrent low

detection levels (IOCL) and two programmable overcurrent high

detection levels (IOCH) for maximum device protection. The two

selectable, simultaneously active overcurrent detection levels,

defined by IOCH and IOCL, are illustrated in Figure 4, page 15.

The eight different overcurrent low detection levels (IOCL0,

IOCL1, IOCL2, IOCL3, IOCL4, IOCL5, IOCL6, and IOCL7) are

illustrated in Figure 4.

If the load current level ever reaches the selected

overcurrent low detection level and the overcurrent condition

exceeds the programmed overcurrent time period (tOCx), the

device will latch the output OFF.

If, at any time, the current reaches the selected IOCH level,

then the device will immediately latch the fault and turn OFF the

output, regardless of the selected tOCLx driver.

For both cases, the device output will stay off indefinitely until

the device is commanded OFF and then ON again.

Reverse Battery

The output survives the application of reverse voltage as low

as -16 V. Under these conditions, the output’s gate is enhanced

to keep the junction temperature less than 150°C. The ON

resistance of the output is fairly similar to that in the Normal

mode. No additional passive components are required.

Ground Disconnect Protection

In the event the 33892 ground is disconnected from load

ground, the device protects itself and safely turns OFF the

output regardless of the state of the output at the time of

disconnection.

Freescale Semiconductor, Inc.

For More Information On This Product,

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